The present invention relates to a method of manufacturing a gas turbine blade retainer and corresponding manufacturing devices therefor. More specifically, the present invention relates to a method of manufacturing a gas turbine blade retainer employing shock absorbing materials and corresponding devices therefor.
The present application is based on Japanese Patent Application No. 2002-095683, which application is incorporated herein in its entirety by reference.
Turbine blades of gas turbines in general, and jet engine turbine blades in particular, are inserted into slots formed on the outer perimeter of disks disposed at the center of the gas turbines. The turbine blades are affixed to respective ones of the disks by blade retainers.
Japanese Patent Application No. Heisei 11-270303 describes a prior art method for affixing the turbine blades. As shown in FIG. 1, an L-shaped retainer 53 formed from a rectangular metal sheet with one end bent, is inserted together with a bucket 54 into a slot 52, a plurality of which are formed on the periphery of a disk 51. It will be noted that the bucket 54 is affixed to the disk 51 by bending the other end of the retainer 53. Additional details regarding the retainer 53 will now be provided while referring to FIG. 2.
In FIG. 2, the retainer 53 is formed from a flat rectangular metal bar having a semi-cylindrical cross section. In general, the retainer 53 is formed from a hard metal such as Inconel. The retainer 53 includes a latch section 56 that is bent at one end almost perpendicularly to a adjacent section 55, which is depicted as a long and narrow bar portion. Furthermore, the opposite end of the retainer 53 includes a bendable piece 57 that possesses a stepped section designed to be bent easily when affixing the bucket 54 to the disk 51.
Formation of the retainer 53 will now be described with reference to FIGS. 3, 4a and 4b, which figures illustrate punching of bar stock material to form a blank and subsequent pressing or bending of the blank into its final form.
As shown in FIG. 3, a flat, long, and narrow bar stock material 62, which is formed in advance by drawing out a bar having a semi-cylindrical cross section, is inserted from the outside of a support 60 into a slot, i.e., a bore, 61 provided at the support 60. It will be appreciated that there are two such supports 59 and 60, which are arranged in a parallel standing condition at a specified interval on a base 58. When the advancing end of the bar stock material 62 comes into contact with the support 59, further movement is prevented. It will also be appreciated that the bar stock material 62 is supported by a receiving die 64 that is freely movable up and down by virtue of the one or more springs 63 (two being depicted) attached between the receiving die 64 and the base 58. It will be noted that the die moves in the downward direction under the impact of a punch 65. One of ordinary skill in the art will recognize that the punch 65 generally possesses a blade width that is equal to the separation between the supports 59 and 60. When the punch 65 drops, the bar stock material 62 is cut into a workpiece, or blank, 75 having the desired dimensions.
As shown in FIG. 4a, the blank 75, which includes distal and proximal ends 75a and 75b, respectively, is then positioned on a bending die 70, with the distal end 75a being in contact with a stop 73. It will be noted that the bending die 70 includes a V-shaped groove 72 that is cut out of the surface supporting the blank at a predetermined angle. A convex punch 71 having a shape that matches the profile of the V-shaped groove 72 of the bending die 70 can then be pressed into the blank 75 from above, causing the blank 75 to bend to form the desired angular shape, as shown in FIG. 4b, to produce a bent blank 76 having distal and proximal ends 76a and 76b. Subsequently, the bendable piece 57, i.e., the portion of the retainer 53 having the stepped profile that is easily bent when affixing the bucket 54 to the disk 51 illustrated in FIG. 2, is formed at the proximal end 76b of the bent blank 76, thereby forming the retainer 53.
It will be appreciated that in manufacturing the prior art retainer 53, when the blank 75 is cut from the bar stock material 62, a displacement of the bar stock material 62 occurs. This displacement causes the cutting punch 65 to stray due to lateral pressure, which, in turn, can cause the blank 75 to jump up or warp, or cause the blank 75 to be scored or marred at various locations between the supports 59 and 60 of the cutting jig or cutting press. Furthermore, die breaks occur due to vibration. In addition, the blank 75 is cut longer than the specified dimensions so that, after cutting, the dimensional accuracy of the blank 75 is poor. It will be noted from the arrangement illustrated in FIG. 3 that the blank 75 can be pressed into the receiving die 64 with sufficient force that it subsequently has to be dislodged from the upper surface of the receiving die 64. Thus, the cutting press illustrated in FIG. 3 suffers from poor production efficiency. Moreover, when the blank 75 was placed onto the bending die 70, there was the problem that the cross-sectional configuration of the blank 75 could collapse, leaving one or more scars 74 on the surface of the bar stock material 62 after bending.
It should be mentioned at this point that Japanese Patent Application No. Heisei 11-270303 is also incorporated herein by reference.